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• iOS Development: Can I store an array of integers in a Core Data object without creating a new table to represent the array?

  - by BeachRunnerJoe

  Hello. I'm using Core Data and I'm trying to figure out the simplest way to store an array of integers in one of my Core Data entities. Currently, my entities contain various arrays of objects that are more complex than a single number, so it makes sense to represent those arrays as tables in my DB and attach them using relationships. If I want to store a simple array of integers, do I need to create a new table with a single column and attach it using a one-to-many relationship? Or is there a more simple way? Thanks in advance for your wisdom!

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• app engine's back referencing is too slow. How can I make it faster?

  - by Ray Yun

  Google app engine has smart feature named back references and I usually iterate them where the traditional SQL's computed column need to be used. Just imagine that need to accumulate specific force's total hp. class Force(db.Model): hp = db.IntegerProperty() class UnitGroup(db.Model): force = db.ReferenceProperty(reference_class=Force,collection_name="groups") hp = db.IntegerProperty() class Unit(db.Model): group = db.ReferenceProperty(reference_class=UnitGroup,collection_name="units") hp = db.IntegerProperty() When I code like following, it was horribly slow (almost 3s) with 20 forces with single group - single unit. (I guess back-referencing force reload sub entities. Am I right?) def get_hp(self): hp = 0 for group in self.groups: group_hp = 0 for unit in group.units: group_hp += unit.hp hp += group_hp return hp How can I optimize this code? Please consider that there are more properties should be computed for each force/unit-groups and I don't want to save these collective properties to each entities. :)

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• Release variable and assigning it again

  - by David Gonrab

  What is the preferred and/or correct way to release an NSMutableString (or any other class for that matter) instance and assign a new instance to the same variable in Objective-C on the iPhone? Currently I'm using [current release]; current = [NSMutableString new]; but I understand that the following works, too. NSMutableString *new = [NSMutableString new]; [current release]; current = [new retain]; [new release]; The variable current is declared in the interface definition of my class and gets released in dealloc.

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• Sharing Eclipse directory on Dropbox between Windows and Mac OS X

  - by sowbug

  This question was close to mine, but not quite. I have a Windows desktop and a MacBook Pro. I'd like to be able to keep my Eclipse workspace in my Dropbox folder. The problem is that many project settings change between platforms: references to JREs, JDKs, and other libs. Every discussion I've seen of this problem seems to suggest taking advantage of the source control system's ignore functionality, so that such-and-such file remains local-only and thus able to remain platform-specific. But when you're working with a real single shared folder, that class of solution doesn't apply. Have you had luck working with a Java Eclipse project living in a single folder shared over the network, cross-platform?

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• Change list link to foreign key change page

  - by Adam

  When viewing the admin change list for a model, is it possible to make the columns that correspond to foreign keys links to their respective pages? A simple example is I have a Foo object which contains Bar as a foreign key. If I'm viewing the admin change list for Foo (and have it set to include Bar in the display_list columns), the main column would link to the Foo instance's edit page while the Bar column would link to the Boo instance's edit page. I understand I can override the template that's used, but I was curious if there was a solution that didn't require that.

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• C++ Singleton design pattern

  - by Artem Barger

  Recently I've bumped into a realization/implementation of the Singleton design pattern for C++. It has looked like this (I have adopted it from the real life example): // a lot of methods are omitted here class Singleton { public: static Singleton* getInstance( ); ~Singleton( ); private: Singleton( ); static Singleton* instance; }; From this declaration I can deduce that the instance field is initiated on the heap. That means there is a memory allocation. What is completely unclear for me is when exactly the memory is going to be deallocated? Or is there a bug and memory leak? It seems like there is a problem in the implementation. My main question is, how do I implement it in the right way?

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• MVC Model architecture

  - by ATT

  I'm getting into CodeIgniter and trying to figure out the good architecture for my models. What kind of models would you create for the following simple example: list page of blog entries: shows part of the entry data, number of comments blog entry page: shows all the entry data, comment list (with part of the comment data) comment page: shows all the comment data I'm trying to get this right so that it's simple and effective. I don't want to load too much information (from the db) on the pages where I don't need them. E.g. should the same entry model handle both multiple entries as well as a single entry? And how should the comments be loaded? I only need the number of comments on the multiple entries (list) page but some of the comment data on the single entry page. How would you handle this?

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• Shared data in an ASP.NET application

  - by Barguast

  I have a basic ASP.NET application which is used to request data which is stored on disk. This is loaded from files and sent as the response. I want to be able to store the data loaded from these files in memory to reduce the number of reads from disk. All of the requests will be asking for the same data, so it makes sense to have a single cache of in-memory data which is accessible to all requests. What is the best way to create a single accessible object instance which I can use to store and access this cached data? I've looked into HttpApplication, but apparently a new instance of this is created for parallel requests and so it doesn't fit my needs.

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• How to test that invalid arguments raise an ArgumentError exception using RSpec?

  - by John Topley

  I'm writing a RubyGem that can raise an ArgumentError if the arguments supplied to its single method are invalid. How can I write a test for this using RSpec? The example below shows the sort of implementation I have in mind. The bar method expects a single boolean argument (:baz), the type of which is checked to make sure that it actually is a boolean: module Foo def self.bar(options = {}) baz = options.fetch(:baz, true) validate_arguments(baz) end def self.validate_arguments(baz) raise(ArgumentError, ":baz must be a boolean") unless valid_baz?(baz) end def self.valid_baz?(baz) baz.is_a?(TrueClass) || baz.is_a?(FalseClass) end end

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• Messaging in local network with .NET

  - by Richard

  Hi All, I need to implement some form of communication mechanism in my application, to send notifications/messages from one application instance to all the others. This is a normal scenario where someone adds and item or deletes and item and you want to notify other users that this has happened. The application runs on the client and connects to a database on the local network. So its not like all clients access a server instance of the application. So from what I know I could use MessageQueues or some form of Database polling where I have a table that stores all the messages (not ideal). Issue is I need to implement this very quickly, so sadly can't go very complex but need the quickest easiest solution. thanks for the help!

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• How to choose programaticaly the column to be querried by Linq using PropertyInfo???

  - by Richard77

  Hello, I would like to control how linq querries my database programaticaly. For instance, I'd like to querry the column X, column Y, or column Z, depending on some conditions. First of all, I've created an array of all the properties inside my class called myPropertyInfo. Type MyType = (typeOf(MyClass)); PropertyInfo[] myPropertyInfo = myType.GetProperties( BindingFlags.Public|BindingFlags.Instance); the myPropertyInfo array allows me to access each property details (Name, propertyType, etc) through the index*[i]* Now, how can I use the above information to control how linq querries my DB? Here's a sample of a querry I'd like to exploit. var myVar = from tp in db.MyClass select tp.{expression}; Expression using myPropertyInfo[i] to choose which property(column) to querry. I'm not sure if that's the way of doing it, but if there's another way to do so, I'll be glad to learn. Thanks for helping.

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• How to retrieve base class only (entity framework)?

  - by Juvaly

  Hi All, I've been scratching my head here for a while now... I have a Consumer class and a BillableConsumer class that inherits Consumer. They are both a part of the Consumers set. The problem is that this following query: Consumer consumer = (from c in _ctx.Consumers where c.ID = id select c).First(); returns a BillableConsumer instance! Just the same as this query: BillableConsumer bconsumer = (from c in _ctx.Consumers.OfType<BillableConsumer>() where c.ID = id select c).First(); How can I return an instance of just the base class? (these are separate tables in the data store).

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• Linq to Sql GroupJoin Paging oddity

  - by OllyA

  I have noticed a strange Sql Translation in a LinqToSql Query I was trying to optimise. If I execute the following Recipients.GroupJoin( RecipientAttributes, x => x.Recipient_Id, y => y.Recipient_Id, (x,y) => new {Recipient = x, Attributes = y}) .Skip(1) .Take(1000) It executes in a single query as expected. However Recipients.GroupJoin( RecipientAttributes, x => x.Recipient_Id, y => y.Recipient_Id, (x,y) => new {Recipient = x, Attributes = y}) .Skip(0) .Take(1000) executes in a separate query for each Attributes selection. Removing the Skip(0) makes no difference either. Can anyone explain this and is there something I can do to get the first page query executing in a single sql statement?

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• How can I find days between different paired rows?

  - by Anthony

  I've been racking my brain about how to do this in one query without PHP code. In a nutshell, I have a table that records email activity. For the sake of this example, here is the data: recipient_id activity date 1 delivered 2011-08-30 1 open 2011-08-31 2 delivered 2011-08-30 3 delivered 2011-08-24 3 open 2011-08-30 3 open 2011-08-31 The goal: I want to display to users a single number that tells how many recipients open their email within 24 hours. E.G. "Users that open their email within 24 hours: 13 Readers" In the case of the sample data, above, the value would be "1". (Recipient one was delivered an email and opened it the next day. Recipient 2 never opened it and recipient 3 waited 5 days.) Can anyone think of a way to express the goal in a single query? Reminder: In order to count, the person must have a 'delivered' tag and at least one 'open' tag. Each 'open' tag only counts once per recipient.

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• TableView problem with Tab Bar!?!?!

  - by Daniel Granger

  I created a tableView which worked fine in a single view app but as soon as I changed the view controller for a Tab Bar Controller and tapped the tab for the view with the table view in I suddenly get this! What has gone wrong? [Session started at 2010-03-28 15:30:15 +0100.] 2010-03-28 15:30:17.763 LogbookTable[13473:207] *** -[UIViewController tableView:numberOfRowsInSection:]: unrecognized selector sent to instance 0x3b14d10 2010-03-28 15:30:17.765 LogbookTable[13473:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[UIViewController tableView:numberOfRowsInSection:]: unrecognized selector sent to instance 0x3b14d10' 2010-03-28 15:30:17.766 LogbookTable[13473:207] Stack: ( 29303899, 2465178889, 29685819, 29255286, 29107906, 4372518, 4379894, 4378891, 3095430, 3035941, 3077376, 3065931, 55820976, 55820399, 55818438, 55817530, 2739877, 2763572, 2745983, 2773089, 37399897, 29088640, 29084744, 2739733, 2777007, 10496, 10350 )

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• Call function from object instantiated in one class in another

  - by Dk43

  I have two classes, both of which need to be able to call the same instance of entitymanager class Engine { EntityManager::Entitymanager EManager; } And I need to add an object to a vector contained by this particular instance of Engine. What I want to do is be able to add a bullet spawned by the player to the vector that contains all my entities. class Player : Entity { void SpawnBullet() {Engine::EManager.Add(BULLET);} } The above returns this error: error: object missing in reference to ‘Engine::EManager’ How do I resolve this? Any help or pointers in the right direction would be much appreciated!

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• Unset array element inside a foreach loop

  - by Richard Knop

  So here is my code: <?php $arr = array(array(2 => 5), array(3 => 4), array(7 => 10)); foreach ($arr as $v) { $k = key($v); if ($k > 5) { // unset this element from $arr array } } print_r($arr); // now I would like to get the array without array(7 => 10) member As you can see, I start with an array of sinwgle key = value arrays, I loop thorugh this array and get a key of the current element (which is a single item array). I need to unset elements of the array with key higher than 5, how could I do that? I might also need to remove elements with value less than 50 or any other condition. Basically I need to be able to get a key of the current array item which is itself an array with a single item.

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• C# LINQ join With Just One Row

  - by Soo

  I'm trying to make a query that grabs a single row from an SQL database and updates it. TableA AId AValue TableB BId AId BValue Ok, so TableA and TableB are linked by AId. I want to select a row in TableB based on AValue using a join. The following query is what I have and only grabs a value from TableB based on AId, I just don't know how to grab a row from TableB using AValue. I know you would need to use a join, but I'm not sure how to accomplish that. var row = DbObject.TableB.Single(x => x.AId == 1) row.BValue = 1; DbObject.SubmitChanges();

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• Django GenericRelation doesn't save related object's id - is this a bug or am I doing it wrong?

  - by pinkeen

  I have a model with a generic relation (call it A), when creating an instance of this object I pass an instance of another model (call it B) as the initializer of the content_object field (via kwargs of the constructor). If I don't save B before creating A then when saving A the content_object_id is saved to the db as NULL. If I save B before passing it to the constructor of A then everything's allright. It's not logical. I assumed that the ID of the related object (B) is fetched when doing A.save() and it should throw some kind of an exception if B isn't saved yet but it just fails silently. I don't like the current solution (saving B beforhand) because we don't know yet if I will be always willing to keep the object, not just scrap it, and there are performance considerations - what if I will add some another data and save it once more shortly after. class BaseNodeData(models.Model): ... extnodedata_content_type = models.ForeignKey(ContentType, null=True) extnodedata_object_id = models.PositiveIntegerField(null=True) extnodedata = generic.GenericForeignKey(ct_field='extnodedata_content_type', fk_field='extnodedata_object_id') class MarkupNodeData(models.Model): raw_content = models.TextField() Suppose we do: markup = MarkupNodeData(raw_content='...') base = BaseNodeData(..., extnodedata=markup) markup.save() base.save() # both records are inserted to the DB but base is stored with extnodedata_object_id=NULL markup = MarkupNodeData(raw_content='...') base = BaseNodeData(..., extnodedata=markup) base.save() markup.save() # no exception is thrown and everything is the same as above markup = MarkupNodeData(raw_content='...') markup.save() base = BaseNodeData(..., extnodedata=markup) base.save() # this works as expected Of course I can do it this way, but it doesn't change anything: base = BaseNodeData(...) base.extnodedata = markup My question is - is this a bug in django which I should report or maybe I'm doing something wrong. Docs on GenericRelations aren't exactly verbose.

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• Rails - inheritance hierarchy of classes where a subtype can play two roles

  - by Miquel

  I need to model Owners and Rentees in an application, so you have stuff that is always owned by someone and can be rented for someone else. I first approached this problem with Single Table Inheritance because both types of person will share all attributes, so you would have a model called Person associated to a table people with Owner and Rentee inheriting from Person. The problem is that Single type inheritance discerns subtypes using a field type and therefore a record in the table can represent either an Owner or a Rentee but not both at the same time, while in the real context you can have an Owner which is renting something from another Owner and therefore that person is at the same time an Owner and a Rentee. How would you approach this problem? Would you use separated tables for owners and rentees? Is there any other type of table inheritance in Rails?

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• Need guidance for my first Android application: how many activities should I use?

  - by jul

  Hi, I'm starting Android doing an application for searching restaurants, and some guidance would be welcome! On the first screen I'd like to have a search field with a submit button (I get the data from a web service), and below a list with the results of the search. When clicking on one of the items of the list it will show a screen with the restaurant details as well as a map showing its location. My questions are: Can I do everything in one single activity or should I do an activity for the search, one for the result list, one for the restaurant description, and another for the map? Would doing one single activity make the application more responsive? How can I use a list and a map within a normal activity (without ListActivity and MapActivity)? Any help, pointer, example application or sample code is very appreciated! Thank you Jul

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• Ruby forwarding method calls

  - by JP

  I have an instance of a master class which generates instances of a subclass, these subclasses need to forward some method calls back to the master instance. At the moment I have code looking something like this, but it feels like I should be able to do the same thing more efficiently (maybe with method_missing?) class Master def initalize(mynum) @mynum = mynum end def one_thing(subinstance) "One thing with #{subinstance.var} from #{@mynum}" end def four_things(subinstance) "Four things with #{subinstance.var} from #{@mynum}" end def many_things(times,subinstance) "#{times} things with #{subinstance.var} from #{@mynum}" end def make_a_sub(uniqueness) Subthing.new(uniqueness,self) end class Subthing def initialize(uniqueness,master) @u = uniqueness @master = master end # Here I'm forwarding method calls def one_thing master.one_thing(self) end def four_things master.four_things(self) end def many_things(times) master.many_things(times,self) end end end m = Master.new(42) s = m.make_a_sub("very") s.one_thing === m.one_thing(s) s.many_things(8) === m.many_things(8,s) I hope you can see what's going on here. I would use method_missing, but I'm not sure how to cope with the possibility of some calls having arguments and some not (I can't really rearrange the order of the arguments to the Master methods either) Thanks for reading!

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• problem with for xml explicit clause in sql server 2005

  - by harrycode

  I am using for xml explicit clause in sql to send table data as xml from sql to asp.net page. I have created a stored procedure when i run store procedure in sql mgmt studio my xml is same as expected. But when I fetch It in asp.net then Xml returned is broken into two rows if xml exceeds certain character limit. I want result to be in single row. I am unable to figure out why single xml string is broken into two rows. please help

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• Custom Global Hotkey Win32 C - Problem

  - by UK

  Hello , I am trying to get the user defined global hot key for my application. Here is my application code, user.rc CONTROL "", IDC_MHOTKEY, HOTKEY_CLASS, WS_TABSTOP, 91, 86, 68, 14 function.cpp WORD wHotKey = SendDlgItemMessage(hwnd, IDC_MHOTKEY, HKM_GETHOTKEY, 0, 0); GLOBAL_HOTKEY= wHotKey; RegisterHotKey ( NULL, TURN_OFF_HOTKEY, HIBYTE(LOWORD(wHotKey)) , wHotKey); main.cpp if ( messages.message == WM_HOTKEY && ( HIWORD ( messages.lParam ) == GLOBAL_HOTKEY) ) alert("Coming only for Single Key"); This code works well, Only If the user selects a single key and not working when he selects multiple key combined like CTRL+F8. I know I am doing something wrong here. Really appreciate If someone guide me in a right path.

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• Is MSDN referencing a system.thread, a worker thread, an io thread or all three?

  - by w0051977

  Please see the warning below taken from the StreamWriter class specification (http://msdn.microsoft.com/en-us/library/system.io.streamwriter.aspx): "Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe." I understand that a W3WC process contains two thread pools i.e. worker threads and I/O threads. A worker thread could contain many threads of its own (if the application creates its own System.Thread instances). Does the warning only relate to System.Threads or does it relate to worker threads and I/O threads as well I.e. as the instance variables of the streamwriter class are not thread safe then does this mean that there would be problems if multiple worker threads access it eg if two users on two different web clients attempt to write to the log file at the same time, then could one lock out the other?

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